1. Field of the Invention
The present invention relates to a magnetic recording medium and a magnetic recording/reproduction apparatus for use in, e.g., hard disk drives.
2. Description of the Related Art
Hard disk drives aim to improve the recording density by using a metal thin-film medium as a magnetic recording medium and an induction head or an MR head (a magnetoresistance head) as a magnetic head. In order for the magnetic recording medium to float on the magnetic head with a high reliability, a protective film is formed on the surface of the magnetic recording medium to improve the lubricating properties and the durability.
Using the MR head as the magnetic head also requires electrical insulating properties, in addition to the durability, in order to prevent short circuits between the metal thin-film medium having conductivity and the MR head. For this purpose, a protective film having a high electrical resistance is formed on the metal thin-film medium, and a protective film having a high electrical resistance is also formed on the magnetic head.
To improve the recording density, it is necessary to narrow the track width and increase the linear recording density. To increase the linear recording density, it is necessary to decrease the magnetic spacing between the magnetic head and the magnetic recording medium, in addition to narrow the head gap of the magnetic head and sharpen the magnetization transition region of the magnetic recording medium. This spacing is calculated from, e.g., the floating amount of the magnetic recording medium from the magnetic head and the thickness of the protective film formed on the magnetic head or the magnetic recording medium. The floating amount of state-of-the-art products is up to 0.07 .mu.m, and up to 0.038 .mu.m has been achieved on the research level. However, if the floating amount is further decreased, the magnetic recording medium and the magnetic head may come in contact with each other while the magnetic recording medium is being driven, and consequently the magnetic recording medium or the magnetic head may be destroyed.
The thickness of the protective film of the magnetic recording medium of the state-of-the-art products is up to 0.02 .mu.m, and up to 0.012 .mu.m is achieved on the research level. However, in the case of the metal thin-film medium it is difficult to further decrease the protective film thickness while maintaining the durability and high electrical resistivity.
If, on the other hand, a medium made from an electrically insulating magnetic substance such as Ba ferrite is used as the magnetic recording medium, no protective film needs to be formed. However, since such an electrically insulating magnetic substance has a small saturation magnetization compared to those of metal magnetic substances, the strength of the signal magnetic field from the medium is significantly low. For this reason, if a magnetic recording medium made from the electrically insulating magnetic substance is used, it is not possible to ensure the sensitivity necessary to obtain a high enough S/N ratio, even with the use of the MR head as the magnetic head, when the track width is further narrowed in the future.
As described above, the present situation is that no magnetic recording medium which satisfies the above characteristics and is suitable for high-density recording has been attained yet.